Deposition cloud tower with adjustable field

ABSTRACT

A cloud tower ( 11 ) receives microscopic particles ( 18 ) impelled by an inert gas ( 17 ) for deposition on a porous substrate ( 29 ) having vacuum ( 34 ) disposed on opposite side. To alter the size and/or shape of the deposition field without changing the entire tower structure, a pair of flaps ( 43, 44 ) are hinged ( 47, 48 ) on one side or on a pair of opposed sides of the cloud primary tower. Another embodiment places selectable tower inserts ( 36, 38 ) within the primary tower structure, fitting therein and sealing thereto.

TECHNICAL FIELD

Mixtures of micron-sized particles, such as platinum and TEFLON®, areimpelled within a cloud deposition tower by means of pressurized inertgas so as to impinge on a target, such as a porous carbon substrate of afuel cell, the gas being drawn off through the pores by vacuum. Thefield of impingement is adjustable by means of hinged walls, orselectable interior wall structures.

BACKGROUND

A common manufacturing process includes the deposition of mixtures ofmicron-sized (microscopic, hereinafter) particles. One example is thedeposition of a mixture of microscopic particles of TEFLON® andcatalyst, such as platinum, on porous carbon substrates used in fuelcells, such as the gas diffusion layer. Another example is diffusion ofmicroscopic carbon and TEFLON® particles on porous carbon substrates soas to provide hydrophobic carbon/carbon substrates (or micro porouslayer).

Herein, the devices that enable the deposition of microscopic particleswill be referred to as a cloud tower, since typical apparatus resemblesa truncated pyramid tower disposed over a vacuum work table, into whichthe microscopic particles are impelled by inert gas, such as nitrogen.

The cloud tower is fed by a tube or other passageway from materialprocessing apparatus. One example is the formation of a slurry of adesired catalyst and TEFLON®. The slurry is then dried to form pellets,and the pellets are ground into microscopic particles. The pellets aredrawn into the hose or other conduit by high pressure inert gas, such asnitrogen, which may be accomplished using an eductor, (sometimes calledan ejector).

The work table is either formed of a suitable mesh or has a substantialnumber of holes therein so as to substantially uniformly apply a vacuumwhich is attached to the bottom of the work table, to attract andthereby distribute the particles throughout the target area, to draw theinert gas through the pores of the substrate being treated, and forexhaust to atmosphere. Typically, the work table, including the vacuumapparatus, may be raised and lowered in order to place the substrateswithin the cloud tower for processing; alternatively, the cloud toweritself may be raised due to suitable flexibility in the tube or otherconduit.

The cloud towers are custom designed in each case to service a selectedsize of a sheet of porous carbonaceous material to be processed.Heretofore, the only way to alter the size of the deposition wouldentail a redesigning of the tower itself in addition to adjusting thepoints of application of vacuum. While the application of vacuum iseasily adjusted, by masking or otherwise, without affecting the processitself (other than the points of application of vacuum), the utilizationof a mask within the cloud tower alters the flow distribution of thecloud of mixed microscopic particles, causing wavelets and otherdistortion in the localized magnitude of distribution. Furthermore,there is local distortion at the mask/substrate interface. These effectseasily result in an unwanted variation in the distribution of theparticles, and therefore a variation in the degree of activity, forinstance, in a substrate having catalyst deposited thereon.

Therefore, means other than the utilization of a mask on a substrate areneeded in order to adjust the size or shape of the field of depositionof microscopic particles.

SUMMARY

Disclosed is a cloud tower which receives microscopic particles impelledby an inert gas for deposition on a porous substrate having vacuumdisposed on a side of the substrate opposite to that on which themicroscopic particles are impinged, with the ability to alter the sizeand/or shape of the deposition field without changing the entire towerstructure.

A first embodiment of the modality herein includes a pair of flapshinged on one side, or on a pair of opposed sides of the cloud tower soas to change the deposition area from a square to a rectangle, or from alarger rectangle to a smaller rectangle or square. Another embodiment isthe utilization of the primary cloud tower together with selectabletower inserts which are smaller than the primary tower structure,fitting therein and sealing thereto, thereby altering the shape and/orsize of the target area. The inserts may provide deposition fields inthe shape of circles, ovals, ellipsis, small squares, smaller squares orrectangles, or otherwise as is desired.

In the utilization of the present modality, masking of the area ofapplication of vacuum may occur with simple masking, because the maskingitself will not alter the cloud deposition process in any way except tolimit the vacuum to the desired field of deposition.

The modality herein may be utilized for the application of anymicroscopic particles or mixtures of particles which are suited topressurized, impelled dispersion onto porous substrates aided by avacuum, as is within the capability of cloud towers in general. Thisincludes mixtures other than those of a catalyst with TEFLON®, or carbonwith TEFLON®; as those are only examples of the modality herein.

Other variations will become more apparent in the light of the followingdetailed description of exemplary embodiments, as illustrated in theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a combination of a partially broken away perspective view ofone example of the modality herein within a typical prior art cloudtower which has been adapted for the present modality, along withconventional material apparatus depicted as blocks.

FIG. 2 is a fragmentary, partially broken away perspective view of thecloud tower of FIG. 1 but having a curvilinear (round, oval orelliptical) tower insert in accordance herewith.

FIG. 3 is a front elevation view of a cloud tower illustrating a commonheight/base aspect ratio.

FIG. 4 is a fragmentary side elevation view of a cloud tower having twohinged flaps extended into an operative position, required for one sideof a pyramid to reduce the area of deposition, in accordance herewith.

FIG. 5 is a front elevation view of the cloud tower of FIG. 4 with theflaps withdrawn from the operative position.

FIG. 6 is a fragmentary, partially broken away rear elevation view ofthe motion rod, push plate and slots.

MODE(S) OF IMPLEMENTATION

Referring to FIG. 1, a cloud tower 11 comprises a truncated pyramid 12of impervious, relatively thin material, such as sturdy sheet steel or asuitable structural plastic. Truncated forms will herein be referred toin terms of their form description, such as the pyramid 12. The pyramid12 has a coupling 15 attaching it to a flexible (or in some casesinflexible) conduit such as a tube 16. The tube 16 receives a mixture ofpressurized inert gas (indicated by arrow 17) and microscopic(micron-sized) particles (indicated by arrow 18) which become thoroughlymixed within the tube 16 and are thereafter impelled through thecoupling 15 and into the pyramid 12.

The mixture of particles is provided by a source 19 of, for example,catalyst and TEFLON®, in a slurry. This is provided to a dryer 21 thatconverts the catalyst and TEFLON® into a mixture of small, dry pellets.The pellets are provided to a grinder 23, which provides microscopicparticles of catalyst and TEFLON® to the tube 16.

The microscopic particles may be ingested into the tube 16 through thesecondary inlet of an eductor not shown (sometimes referred to as anejector), the primary inlet to which is attached to pressurized inertgas, or in some other conventional fashion. The pressure of the gas neednot be much above atmospheric but simply enough to impel the pelletsthrough the tube 16 and into the tower 11.

The pyramid has flanges 27 which may include soft seals, which rest onthe target, such as a porous substrate 29, which in turn is carried by awork station table 31. In the present example, the porous substrate 29is carbon. The work station table 31 is either a mesh or has numerousholes therein throughout the intended deposition area so as to providevacuum to the interior of the pyramid 12, as represented by the arrow34. The vacuum assists in dispersing the microscopic particlesthroughout the area within the pyramid 12, thereby to cover the entireintended portion of the porous substrate 29. The vacuum also draws theinert gas away from the substrate surface so as to allow the continuumof impingement to occur.

The description thus far is of a microscopic particle cloud depositiontower apparatus known to the art. In accordance with the modalityherein, however, there is provided a tower insert 36, which in this caseis also a pyramid. Although the pyramid 12 (referred to hereinafter asthe primary pyramid 12) is typically a square pyramid in the prior art,the shape thereof is immaterial to the modality herein. Similarly,pyramid-shaped tower insert 36 in accordance with the modality hereinmay be square or rectangle despite the shape of the primary pyramid 12,so long as the selected tower insert 36 will fit therein. The size ofthe selected tower insert may also vary as desired.

FIG. 2 is a portion of the view in FIG. 1, except that, within theprimary pyramid 12, there is a selected tower insert 38 which iscurvilinear, and which could either be conical, as in FIG. 2, or otherconoids such as ellipses and ovals as desired. Furthermore, the selectedtower insert may be of another shape. In the embodiments of FIGS. 1 and2, the coupling 15 is adapted to receive similar but smaller couplingswhich may have a key to align the selected inserts' coupling with thecoupling 15 to ensure that the tower insert is properly aligned with thetarget, porous substrate 29. Otherwise, an equally effective means foralignment may be provided.

FIG. 3 shows an approximate illustration of the height to base-widthaspect ratio, which typically may be on the order of 2.5 to 1. However,for clarity of exemplary details, the disclosure herein illustratespyramids having aspects closer to 1 to 1, or less.

In another embodiment, two flaps 43, 44 are able to swing between aninoperative position, as in FIG. 4 and an operative position shown inFIG. 5. The flap 44 is against the flap 43 and the flap 43 is againstthe pyramid wall 45. The motion between these two positions does notcause any gaps between the outer edges of the flaps 43, 44 andrespective walls 56, 57 of the primary pyramid 12 a because the hinges47, 48 are at exact right angles (90°) with respect to the correspondingwalls 56, 57.

Referring to FIGS. 4 and 5, a pair of flaps 43, 44 are disposed againstone wall 45 of a primary pyramid 12 a by respective hinges 47, 48. InFIG. 5, the flaps 43, 44 are shown in the operative position with thebottom edges resting on (or near) the substrate. The hinge 47 is mountedto the wall 45 below the hinge 48 so that the flap 43 will be behind theflap 44. The purpose is so that once the flaps are brought forward intothe operative position as illustrated in FIG. 5, they will overlapsufficiently to provide a seal.

The flaps 43, 44 are moved into the operative position shown in FIG. 5by a positioning mechanism 60 which pushes a rod 62 inwardly as shown byan arrow 63. The rod 62 is fastened to a push plate 66 such as bywelding or brazing, and is also fastened at its rightmost end to theflap 44. Thus, the push plate 66 pushes the two flaps to the operativeposition, and since it is fastened to the flap 44, will pull the flap 44and therefore the flap 43 back into the inoperative position, the pushplate 66 nesting into a void 68 of the appropriate size in the wall 45.Since the flaps 43, 44 cover the void, it can be ample without worryingabout a seal, or a seal may be provided.

A soft seal may be placed along the back of flap 44 and along the frontof the flap 43 where such seals could touch the opposing flap, asdesired in any given implementation of the modality herein. However,such seals may generally be unnecessary. Further, when the flaps are inthe operative position as shown in FIG. 5, the vacuum may be limited tothe area below and to the right of the flaps 43, 44 (as seen in FIG. 5),such as by masking, if desired in any given implementation. Therefore,between the cloud pressure tending to push on the flap 44 and theresistance provided to the flap 43 by the positioning mechanism 60 bythe rod 62, depending on the pressure of the incoming flow and of thevacuum, there should be no need for seals. There may or may not be anyseals, in any event.

Referring to FIG. 6, the view from the left side of the flaps 43, 44 (asseen in FIG. 5) shows the push plate 66 broken away to reveal the rod 62which may be welded, or even screwed (from the right to the left) for atight fastening to the flap 44. Since both rotate at the same timeeither into or out of the operative position, there is no relativeup/down motion between any given points on the flaps. Thus, the onlyrelative motion between the flaps 43, 44 is horizontal.

To accommodate the horizontal movement between the two flaps as theymove to and from the operational position, a slot 71 is provided in theflap 43, to allow horizontal motion of the rod 62 as the flap 44, towhich it is fastened, moves back and forth horizontally, as both flapsmove up or down, due to the non-horizontal position of the hinges 47,48. The rod 62, push plate 66 and slot 71 are shown in FIG. 6 in phantomin their respective positions when the flaps 43, 44 are in theinoperative position. As the rod moves back and forth to adjust thepositions of the flaps, the push plate 66 will only move a few inches,such as less than three inches in the example illustrated in FIGS. 4-6.This will cause the rod to move sideways less than about two inches inthe example.

In this embodiment, the hinges 47, 48 are disposed directly to theprimary pyramid 45. Obviously, if the flaps 43, 44 were wider, the slot71 longer, and the hinges slideable upwardly, then the target area onthe substrate 29 could be reduced further. With shorter but wider flapsand hinges slideable downwardly, that would permit having the degree oftarget area illustrated in FIG. 5 but with shorter flaps (as justdescribed above). Thus, infinite positioning over a finite range oftarget area may be achieved.

The foregoing has been described with respect to flaps 43, 44 disposedon a single wall 45. Similar flaps may be disposed on a wall opposite tothe wall 45 as desired, to provide further adjustment to the target sizeand shape, as well as positioning of the target.

The description referring to FIGS. 1 and 2 shows that means, includingwall structure in addition to the wall structure of the primary cloudtower, may be tower inserts of various shapes and sizes, such as pyramidinsert 36, cone insert 38 and so forth. The description referring toFIGS. 4-6 shows that such means may be hinged flaps, such as flaps 43,44.

Since changes and variations of the disclosed embodiments may be madewithout departing from the concept's intent, it is not intended to limitthe disclosure other than as required by the appended claims.

1. Apparatus, comprising: a source of microscopic particles impelled byinert gas; a porous substrate which is to receive the microscopicparticles; a primary cloud tower connected to the source, resting on thesubstrate to define the target area thereon for the particles, andhaving wall structure completely surrounding all volume between thesubstrate and the connection to the source; and a vacuum applied to aside of the substrate opposite to the side engaged by the primary cloudtower; characterized by: means including wall structure in addition tothe wall structure of the primary cloud tower for changing the wallstructure surrounding the volume and for changing the target area forthe particles.
 2. Apparatus according to claim 1 further characterizedin that: the distance between the substrate and the top of the cloudtower where connected to the source being at least twice the dimensionof the tower across the substrate.
 3. Apparatus according to claim 1further characterized in that: said means includes a selected one of aplurality of cloud tower inserts which fit within said primary cloudtower and connect to the source.
 4. Apparatus according to claim 1further characterized in that: the primary cloud tower is a pyramid withthe connection at its apex and the substrate at its base.
 5. Apparatusaccording to claim 4 further characterized in that: said means includesat least one pair of flaps hinged to a wall of the primary cloud tower.6. Apparatus according to claim 5 further characterized in that: eachpair of flaps are hinged to the related wall by hinges which areslideable along the related wall, each in a direction perpendicular toits bending axis.